Elastic endless crawler

ABSTRACT

In an elastic endless crawler comprising an annular belt-shaped elastic crawler body, according to the present invention, the crawler body comprises a series of driven elements for operation of the crawler and a reference plane, which reference plane passes through respective centers of the drive elements and extends in a longitudinal direction of the crawler, and a thickness of one side relative to the reference plane and a thickness of the other side relative to the reference plane are different from one another. Preferably, lengths between respective crawler body end surfaces facing in a crawler widthwise direction, and the reference plane are different from one another. Further, preferably, a thickness of one side, which is shorter in length, of the crawler body is greater than that of the other side, which is longer in length, of the crawler body.

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to an elastic endless crawler.

BACKGROUND ART

[0002] A rubber crawler, which is mounted on a motor vehicle such as anearth-moving vehicle, as shown in FIGS. 7 and 8, presents an endlessbelt shape. The illustrated rubber crawler 101 is basically formed of acrawler body 103 that is made of rubber. The rubber crawler 101 isentrained around a drive roller 105 and an idler roller 107. A pluralityof take-up rollers 109 is disposed at an inner peripheral side of therubber crawler 101.

[0003] A number of cores 111 are embedded in the crawler body 103 withpredetermined spacing along a longitudinal direction of the rubbercrawler. The cores 111 extend in a direction orthogonal to the rubbercrawler longitudinal direction (i.e., a widthwise direction of therubber crawler) and are disposed parallel with one another. A number ofengagement holes 7 (sprocket holes) are formed in the crawler body andrespectively disposed between two adjacent cores. Teeth of the driveroller (sprocket) engage with the engagement holes.

[0004] Projections 111A of the cores 111 protrude from the rubbercrawler inner peripheral surface.

[0005] Cord layers are provided at posterior positions (at an outerperipheral side) on each side in the rubber crawler widthwise direction.Each cord layer is comprised of a plurality of steel cords C, each ofwhich extends along the rubber crawler longitudinal direction and whichare embedded parallel with one another.

[0006] A plurality of lugs 115 are regularly provided at predeterminedpitches in the rubber crawler longitudinal direction, each lug extendingfrom the outer peripheral surface of the rubber crawler 101. All thelugs are integrally formed with crawler body 115.

[0007] Such a conventional type rubber crawler generally has a shape orstructure which is symmetrical in relation to the sprocket holes (arubber crawler longitudinal center line). However, recently, a rubbercrawler, which has an asymmetrical structure, has appeared. It isresulted from the fact that forming positions of sprocket holes arerespectively shifted from widthwise direction center positions to oneside due to an increase in crawler width based on the tendency ofvehicles to become large. A thickness (rubber thickness) of a left sideportion of a crawler body and a thickness (rubber thickness) of a rightside portion of the crawler body are the same as in the conventionalsymmetrical type rubber crawler as described above.

[0008] In such an asymmetrical type rubber crawler, a body portion andlugs, which are located at a shorter side, with regard to a lengthbetween a sprocket hole center and a side end face, of a crawler body,are damaged more easily than those located at a longer side of thecrawler body. In other words, there is a concern that a rubber-madecrawler body portion located at a weakened side might be unilaterallydamaged or worn out. It is considered that this is because the areas ofleft and right portions of a rubber crawler, to which portions loads areapplied when the rubber crawler is being used, are different from eachother, and accordingly, the surface pressure differs between the leftand right portions.

[0009] With respect to this problem, a convenient solution isconceivable in which ground contacting areas at left and right portionsof lugs are made approximately equal. However, difficulties areexperienced in designing a rubber crawler having such a structure.

[0010] Thus, it is generally said that asymmetrical type rubber crawlershave a short life.

DISCLOSURE OF THE INVENTION

[0011] In light of the above-described problems, the present inventionhas been invented. One object of the invention is to provide an improvedcrawler having excellent durability and reliability or having a longlife, in which a substantial difference in strength between one side ina widthwise direction (a left and right direction) of an asymmetricaltype elastic endless crawler and the other side in the widthwisedirection of the crawler can be eliminated or both of the sides of thecrawler can have the same level of strength.

[0012] In order to solve the above-described problems, according to thepresent invention, there is provided an elastic endless crawlercomprising an annular belt-shaped elastic crawler body characterized inthat: the crawler body comprises a series of driven elements foroperation of the crawler and a reference plane, which reference planepasses through respective centers of the drive elements and extends in alongitudinal direction of the crawler; and a thickness of one siderelative to the reference plane and a thickness of the other siderelative to the reference plane are different from one another.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a sectional view transversely of the length of a rubbercrawler according to an embodiment of the present invention.

[0014]FIG. 2 is a side view of the rubber crawler.

[0015]FIG. 3 is a view of the rubber crawler as seen from an innerperipheral side thereof.

[0016]FIG. 4 is a view of the rubber crawler as seen from an outerperipheral side thereof.

[0017]FIG. 5 is a copy of an external appearance of an example of arubber crawler after an endurance test has been performed.

[0018]FIG. 6 is a copy of an external appearance of a comparativeexample of a rubber crawler after the endurance test performed.

[0019]FIG. 7 is a side view showing a conventional rubber crawlercurrently in use.

[0020]FIG. 8 is a partly-broken, perspective view of a conventionalrubber crawler.

BEST MODE FOR CARRYING OUT THE INVENTION

[0021] An embodiment of the invention will be hereinafter described withreference to FIGS. 1 to 4. However, the present invention is not limitedthereto.

[0022] An illustrated rubber crawler 1 presents an endless belt form andincludes a crawler body 3 that is made of rubber. A plurality of steelcores 5 are embedded in the crawler body 3 with predetermined intervals(or pitches) along a longitudinal direction of the rubber crawler. Thecores 5 extend individually in a direction orthogonal to the rubbercrawler longitudinal direction (i.e., a widthwise direction of therubber crawler) and are disposed parallel with one another. Engagementholes 7 (or sprocket holes) are formed in the crawler body andrespectively disposed between two adjacent cores.

[0023] A plurality of lugs 11 are regularly provided in a protrudingmanner at an outer peripheral surface of the rubber crawler withpredetermined intervals along the rubber crawler longitudinal direction.The lugs 11 are integrally formed with the crawler body 3. These lugs 11can be divided by a reference plane A as a boundary into two groups oflugs 11: one group of lugs on the right side in FIG. 4 and the othergroup of lugs on the left side in the same figure. The lugs 11 of theright side lug group and the lugs 11 of the left side lug group aredifferent from one another in size and shape and are disposed in anoffset manner with respect to the rubber crawler longitudinal direction.In other words, the lugs 11 are generally disposed in a staggeredmanner. The intent of this disposition is to reduce generation ofvibration or noise. Incidentally, the lugs 11 are not limited to theillustrated shapes and may have any appropriate shapes.

[0024] Here, a surface, which passes through each center of theengagement holes 7 and extends in the rubber crawler longitudinaldirection, is defined as the reference plane A. One side with respect tothe reference plane A, for example, in the illustrated embodiment theright side including longer part of the crawler body, is denoted by Wand the other side, i.e., the left side including shorter part of thecrawler body, is denoted by N (refer to FIG. 1).

[0025] Each of the cores 5 is arranged approximately in pointsymmetrical relation with respect to a center between the engagementholes 7 on both sides thereof and has two raised portions (bosses) 5 aand 5 b, which protrude from an inner peripheral surface of the rubbercrawler, and wing portions 5 c and 5 d, which extend to respectivesides, i.e., left (N) side and right (W) side, respectively. Fittingportions (i.e., a fitting concave portion 5 e and a fitting convexportion 5 f) are provided one at each side of each of the cores 5, foran interconnection with adjacent cores.

[0026] A dimension S_(W) between the reference plane A and the end faceof the right side wing portion 5 d is greater than a dimension S_(N)between the reference plane A and the end face of the left side wingportion 5 c (S_(W)>S_(N)). Similarly, a dimension W_(W) between thereference plane A and the right end of the crawler body is greater thana dimension W_(N) between the reference plane A and the left end of thecrawler body (W_(W)>W_(N)).

[0027] The left side wing portion 5 c and the right side wing portion 5d of each of the cores 5 include tracker roller travelling portions(travelling surfaces) 5 g of rectangular shape, which are exposed to theinner peripheral side of the rubber crawler and which are substantiallycoplanar with the inner peripheral surface of the rubber crawler.

[0028] Grooves 13 are formed at the rubber crawler inner peripheralportion between each of two adjacent cores in order to reduce a windingresistance when the rubber crawler is being wound. Each groove 13 isformed until the vicinity of the tracker roller travelling portion 5 g.However, it may be formed until the edge of the rubber crawler widthwisedirectional end.

[0029] As can be seen from FIG. 1, cord layers are formed and positionedbehind or beneath the respective cores 5 (at the rubber crawler outerperipheral side), more specifically, behind or beneath the left sidewing portions 5 c and the right side wing portions 5 d. Each of the cordlayers includes a plurality of steel cords C, each of which extendsalong the rubber crawler longitudinal direction and which are embeddedparallel with one another.

[0030] A dimension H_(N) between a cord center of one cord group and therubber crawler inner peripheral surface and a dimension H_(W) between acord center of the other cord group and the rubber crawler innerperipheral surface are substantially the same (H_(N)≈H_(W)). However, adimension TN between the cord center of the one cord group and therubber crawler outer peripheral surface and a dimension T_(W) betweenthe cord center of the other cord group and the rubber crawler outerperipheral surface are different from each other (T_(N)≠T_(W),T_(N)>T_(W), or (H_(N)+T_(N))≠(H_(W)+T_(W))).

[0031] The present inventor conducted a wide variety of experiments inconnection with relations between T_(N) and T_(W) to accomplish the enddesired. Finally, he has found that it is possible to obtain the desiredeffect by determining dimensions of rubber crawler components such thatat least one of the following three formula is satisfied or achieved.

T _(N) /T _(W)≦(W _(W) +W _(N))^(0.5) /W _(W) ^(0.5)  (1)

T _(N) /T _(W)≦(S _(W) +S _(N))^(0.5) /S _(W) ^(0.5)  (2)

T _(N) /T _(W)≦(L _(W) +L _(N))^(0.5) /L _(W) ^(0.5)  (3)

[0032] wherein

[0033] T_(N)=a length dimension between the cord center at the N sideand the rubber crawler outer peripheral surface;

[0034] T_(W)=a length dimension between the cord center at the W sideand the rubber crawler outer peripheral surface;

[0035] W_(W)=a length dimension between the reference plane A and the Wside end surface of the crawler body;

[0036] W_(N)=a length dimension between the reference plane A and the Nside end surface of the crawler body;

[0037] S_(W)=a length dimension between the reference plane A and the Wside core end surface;

[0038] S_(N)=a length dimension between the reference plane A and the Nside core end surface;

[0039] L_(W)=a length dimension between the reference plane A and the Wside lug edge; and

[0040] L_(N)=a length dimension between the reference plane A and the Nside lug edge.

[0041] T_(N) and T_(W), which can be calculated from the above formula,should be determined such that a difference therebetween isapproximately 2 to 15 mm. That is, in a case in which this difference isover 15 mm, a great difference in height between left and right lugs ofa rubber crawler may exist, and therefore, this may have a deleteriouseffect on a driving force of a vehicle in which the rubber crawler ismounted. On the other hand, in a case in which the above difference isbelow 2 mm, there is a concern that it is not possible to accomplish theend desired.

[0042] Lastly, brief description will be given of an endurance test,which was carried out in order to verify a performance of a rubbercrawler according to the present invention.

[0043] A rubber crawler (example) in which T_(N)−T_(W)=10 mm and arubber crawler (comparative example) in which T_(N)=T_(W) were used inan experiment. In both of the rubber crawlers, each lug has a hardnessof approximately 70 degrees and an elongation of 400% or more, and eachbody portion (rubber portion) on an inner peripheral side (trackerroller side) has a hardness of approximately 74 degrees and anelongation of 200% or more.

[0044] In the experiment, test vehicles in which respective rubbercrawlers were mounted were prepared and driven under the followingtravelling conditions. Thereafter, the rubber crawlers were inspectedfor an external appearance.

[0045] The experimental travelling conditions were such that each of thetest vehicles was driven for 50 hours or through 5 cycles, wherein, inone cycle, the vehicle was driven for 8 hours on a rough road in azigzag driving manner, for 1 hour on a metaled road in a zigzag drivingmanner, for fifteen minutes on a cobbled road in a figure-of-eightdriving manner, and for forty-five minutes on a concrete road in azigzag driving manner.

[0046] As can be seen from FIG. 5 which is a copy of an externalappearance of the example of the rubber crawler after the travelling,although wear has resulted in surfaces of lugs, it is not excessive, andthere is almost no serious or major crack. Serious cracks did not occurin crawler body surface portions each between two adjacent lugs.

[0047] On the other hand, as can be seen from FIG. 6 which is a copy ofan external appearance of the comparative example of the rubber crawlerafter the travelling, considerable wear has resulted in surfaces oflugs. The shapes of the lugs have been substantially deformed and somelugs have been partly fractured. Further, there are portions where cordlayers, which must have been embedded within the crawler body, arepartly subjected outside.

[0048] Additionally, during the experimental travelling, the number ofoccurrences of running off of the rubber crawler (the example) was zero,whereas the number of occurrences of running off of the rubber crawler(comparative example) was six.

INDUSTRIAL APPLICABILITY

[0049] As described above, according to the present invention, it ispossible to effectively avoid or reduce a potential disadvantage thatone side in a widthwise direction of an asymmetrical rubber crawler iseasily damaged. As a result, a long life rubber crawler that islow-priced and superior in durability and reliability can be placed onthe market within a short period of time.

1. An elastic endless crawler comprising an annular belt-shaped elasticcrawler body characterized in that: the crawler body (3) comprises aseries of driven elements (7) for operation of the crawler and areference plane (A), which reference plane passes through respectivecenters of the drive elements (7) and extends in a longitudinaldirection of the crawler; and a thickness of one side relative to thereference plane (A) and a thickness of the other side relative to thereference plane are different from one another.
 2. The elastic endlesscrawler of claim 1, wherein lengths between respective crawler body endsurfaces, said surfaces facing in a crawler widthwise direction, and thereference plane (A) are different from one another.
 3. The elasticendless crawler of claim 2, wherein a thickness of one side, which isshorter in length, of the crawler body (3) is greater than a thicknessof the other side, which is longer in length, of the crawler body (3).4. The elastic endless crawler of claim 1, wherein a plurality of cords(C) for reinforcement are embedded at the respective sides or left andright sides relative to the reference plane (A) in the crawler body (3)such that the cords extend in the crawler longitudinal direction and arespaced apart along the crawler widthwise direction with a predeterminedspacing.
 5. The elastic endless crawler of claim 4, wherein lengthsbetween respective crawler end surfaces in a crawler widthwise directionand the reference plane (A) are different from one another and whereinwhen one side, which is shorter in length, is referred to as a N sideand the other side, which is longer in length, is referred to as a Wside and when a length dimension between a cord center at the N side andan outer peripheral surface of the crawler body (3) is T_(N), a lengthdimension between a cord center at the W side and the outer peripheralsurface of the crawler body (3) is T_(W), a length dimension between thereference plane (A) and the N side crawler body end surface is W_(N),and a length dimension between the reference plane (A) and the W sidecrawler body end surface is W_(W), T _(N) /T _(W)≦(W _(W) +W _(N))^(0.5)/W _(W) ^(0.5).
 6. The elastic endless crawler of claim 4, wherein aplurality of cores (5) are embedded in the crawler body (3) withpredetermined intervals along the crawler longitudinal direction suchthat the cores (5) extend individually in the crawler widthwisedirection, which is orthogonal to the crawler longitudinal direction,and are disposed parallel with one another.
 7. The elastic endlesscrawler of claim 6, wherein the driven elements (7) comprise sprocketengaging holes (7), each of which is formed in the crawler body anddisposed between two adjacent cores (5).
 8. The elastic endless crawlerof claim 6, wherein lengths between respective crawler end surfaces in acrawler widthwise direction and the reference plane (A) are differentfrom one another and wherein when one side, which is shorter in length,is referred to as a N side and the other side, which is longer inlength, is referred to as a W side and when a length dimension between acord center at the N side and an outer peripheral surface of the crawlerbody (3) is T_(N), a length dimension between a cord center at the Wside and the outer peripheral surface of the crawler body (3) is T_(W),a length dimension between the reference plane (A) and a core endsurface at the N side is S_(N), and a length dimension between thereference plane (A) and a core end surface at the W side is S_(W), T_(N) /T _(W)≦(S _(W) +S _(N))^(0.5) /S _(W) ^(0.5).
 9. The elasticendless crawler of claim 4, wherein a plurality of lugs (11) areregularly provided in a protruding manner at an outer peripheral surfaceof the crawler body (3) with predetermined intervals along the rubbercrawler longitudinal direction.
 10. The elastic endless crawler of claim9, wherein lengths between respective crawler end surfaces in a crawlerwidthwise direction and the reference plane (A) are different from oneanother and wherein when one side, which is shorter in length, isreferred to as a N side and the other side, which is longer in length,is referred to as a W side and when a length dimension between a cordcenter at the N side and the outer peripheral surface of the crawlerbody (3) is T_(N), a length dimension between a cord center at the Wside and the outer peripheral surface of the crawler body (3) is T_(W),a length dimension between the reference plane (A) and a lug edge at theN side is L_(N), and a length dimension between the reference plane (A)and a lug edge at the W side is L_(W), T _(N) /T _(W)≦(L _(W) +L_(N))^(0.5) /L _(W) ^(0.5).